A Spinal Cord Stimulator (SCS) is used to exert pulsed electrical signals to the spinal cord to control chronic pain. Spinal cord stimulation, in its simplest form, comprises stimulating electrodes implanted in the epidural space, an implantable pulse generator implanted in the lower abdominal area or gluteal region, conducting wires connecting the electrodes to the electrical pulse generator, an electrical pulse generator remote control, and an electrical pulse generator charger. Spinal cord stimulation has notable analgesic properties and, at the present, is used mostly in the treatment of failed back surgery syndrome, complex regional pain syndrome and refractory pain due to ischemia.
Electrotherapy of pain by neurostimulation began shortly after Melzack and Wall proposed the gate control theory in 1965. This theory proposed that nerves carrying painful peripheral stimuli and nerves carrying touch and vibratory sensation both terminate in the dorsal horn (the gate) of the spinal cord. It was hypothesized that input to the dorsal horn of the spinal cord could be manipulated to “close the gate” to the nerves. As an application of the gate control theory, Shealy et al. implanted the first spinal cord stimulator device directly on the dorsal column for the treatment of chronic pain in 1971.
Spinal cord stimulation does not eliminate pain. The electrical impulses from the stimulator override the pain messages so that the patient does not feel the pain intensely. In essence, the stimulator masks the pain. A trial implantation is performed before implanting the permanent stimulator. The physician first implants a trial stimulator through the skin (percutaneously) to perform stimulations as a trial run. Because a percutaneous trial stimulator tends to move from its original location, it is considered temporary. If the trial is successful, the physician can then implant a permanent stimulator. The permanent stimulator is implanted under the skin of the abdomen with the leads inserted under the skin and subcutaneously fed to and inserted into the spinal canal. This placement of the stimulator in the abdomen is a more stable, effective location. The leads, which consist of an array of electrodes, can be percutaneous type or paddle type. Percutaneous electrodes are easier to insert in comparison with paddle type, which are inserted via incision over spinal cord and laminectomy.
There are a number of problems that exist in currently available implantable pulse generators that limit the full benefits of dorsal column stimulation from an effectiveness and patient user friendly perspective.
One problem is that the circuits in the current generators consume too much power. This requires frequent recharging, making it very inconvenient for patients. Another problem is that the current generators are limited in concurrently generating different stimulation patterns to treat different parts of the body simultaneously. Accordingly, when patients have varying degrees of pain in different parts of the body, it is difficult, if not impossible, to affectively treat all area of pain. Still another problem is that in order to recharge a battery of the implantable pulse generator, there needs to be proper alignment of the implantable pulse generator and an external charger that induces power to the implantable pulse generator for recharging the battery.
Therefore, it would be desirable to provide a system and method for generating stimulation patterns and determining proper alignment between the implantable pulse generator and the external charger which resolve the problems discussed above.